There are two primary objectives of this work. An intestinal lipodystrophy was described in gerbils fed purified diets. The disease is characterized by the accumulation of large amounts of lipid in the mucosal cells of the small intestine. It is much more severe in females than in males, is much more severe when the diet contains saturated fat than when it contains unsaturated fat, and is prevented by the feeding of crude materials such as liver extract and yeast. Studies to date have demonstrated that the unknown material which prevents the lesion is inositol. These studies are directed toward the determination of the requirement of inositol under various dietary conditions and the role of inositol in the function of the mucosal cells. The second objective is to further study the role of various fats in the control of lipid and cholesterol metabolism. Data obtained to date indicate that diets high in saturated fats produce metabolic patterns in male gerbils similar to those obtained with low-fat, high- carbohydrate diets. The incorporation of various labeled substrates into various lipid fractions by tissues from animals fed diets varying in kind and amount of fat and carbohydrate will be studied. In vitro liver perfusion, liver slices and mucosal scrapings will be used. Turnover rate of cholesterol in animals labeled with C14-cholesterol and fed the various diets will also be included and infant monkeys fed high fat formula diets will also be utilized to evaluate the effects of various kinds of fat upon serum cholesterol regulation.